Method for thermal ablation of hollow body organs

ABSTRACT

Hollow body organs, such as the gallbladder, may be ablated by introducing a substantially unheated thermally conductive medium to the interior of the organ. The thermally conductive medium is then heated to a temperature sufficient to necrose the endothelial lining or mucous membrane of the organ. After the lining or membrane has necrosed, the interior of the organ will fibrose over time and the organ will eventually be resorbed by the body. A catheter useful in performing the ablation method comprises an elongate member having a heating element at its distal tip. The catheter will include at least one lumen for delivering the thermally conductive medium to the interior of the hollow body organ, and the heating means is used to raise the temperature of the thermally conductive medium after it has been delivered. Optionally, the catheter may include one or more inflatable balloons which facilitate sealing of the hollow body organ to inhibit leakage of the thermally conductive medium during the treatment process. The heating element may comprise a single point heat source or a heat source distributed over a fixed length. Distributed heat sources may further be adapted to provide for a non-linear heat flux delivery pattern.

This application is a continuation-in-part of application Ser. No.07/529,077, filed May 25, 1990, now U.S. Pat. No. 5,100,388, which was acontinuation-in-part of application Ser. No. 07/407,839, filed Sep. 15,1989, now U.S. Pat. No. 5,045,056, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to methods and apparatus for thethermal ablation of hollow body organs, such as the gallbladder. Inparticular, the present invention relates to a catheter structure havinga heating element at its distal end, where the catheter may be used tointroduce an unheated thermally-conductive medium to the hollow bodyorgan, and the heating element used to heat the medium in situ in orderto destroy the endothelial lining or mucous membrane of the organ.

Heretofore, it has frequently been necessary to perform open surgery inorder to remove diseased body organs, such as gallbladders, appendixes,and the like. For example, the current treatment for cholecystolithiasis(gallstone disease) involves the surgical removal of the gallbladder,referred to as a cholecystectomy. As with all major surgical procedures,the patient is exposed to the risk of trauma, infection, generalanesthetic, as well as requiring extended recuperation time. It wouldtherefore be desirable to provide for therapies for diseased organswhich can effectively eliminate the organ without the necessity of opensurgical intervention.

In recent years, a number of therapies have been developed as analternative to open surgery, often referred to as "least invasivesurgery." While least invasive surgical procedures have no fixeddefinition, they are generally characterized by the use of specializedsurgical tools in combination with visual or radiographic imagingtechniques. The specialized tool is generally inserted through an openbody orifice or a small surgical incision, and the tool is thenpositioned within the body using the imaging technique to allowmanipulation of the affected organ or structure. A common example ofleast invasive surgery is arthroscopic knee surgery where penetration ofthe surgical tools is minimal. Less accessible body organs, such as theheart and interior blood vessels, may be reached by specializedcatheters which may be routed through the vascular system overrelatively long distances. Typical of such vascular catheters areballoon dilatation catheters which are used to expand regions ofstenosis within diseased blood vessels.

For the above reasons, it would be desirable to provide least invasivesurgical methods and apparatus for the destruction or ablation ofdiseased hollow body organs, such as the gallbladder, the appendix, theuterus, and the like. Such methods and apparatus should also be suitablefor the treatment of relatively small body structures, such as bloodvessels, and should be able to effect ablation without undue risk tosurrounding body tissues and structures. In particular, the method andapparatus should be able to provide for the controlled application ofthermal energy in order to destroy the hollow body organ with a minimalchance of regeneration. Desirably, the apparatus should be sufficientlysmall and flexible to allow introduction through and into constrictedducts and passages adjoining the hollow body organ, and the apparatusshould be capable of delivering a non-linear heat flux which variesdepending on position within the hollow body organ and/or connectingduct. Such non-linear heat flux will allow control of the amount of heatdelivery to particular regions within the organ and/or duct.

2. Description of the Background Art

Coleman, Non-Surgical Ablation of the Gallbladder, Proc. 1988 SCVIR, pp214-219, is a review article discussing various techniques fornon-surgical gallbladder ablation, including the work of Salomonowitzand of Getrajdman relating to the introduction of an externally heatedmedium to induce fibrosis of the gallbladder. The article furtherpresents data demonstrating thermal ablation of a dog's gallbladderafter open surgical injection of hot contrast media. The work ofSalomonowitz is described in Salomonowitz et al. (1984) Arch. Surg.119:725-729. The work of Getrajdman is described in Getrajdman et al.(1985) Invest. Radiol. 20:393-398 and Getrajdman et al. (1986) Invest.Radiol. 21:400-403. The use of sclerosing agents to induce gallbladderfibrosis is described in Remley et al. (1986) Invest. Radiol.21:396-399. See also Becker et al. (1988) Radiology 167:63-68. U.S. Pat.No. 4,160,455, describes a device for internally heating a body cavityfor therapy, where the heat is intended to inhibit the growth of tumorcells. German Patent 37 25 691 describes a catheter combining a heaterat its distal tip and a balloon proximate the heater, where the heateris not directly exposed to the fluid environment surrounding thecatheter tip. U.S. Pat. No. 4,869,248, describes a thermal ablationcatheter having a resistive heating loop at its distal end. Other patentdocuments describing heated or cooled catheters include U.S. Pat. Nos.4,676,258; 4,638,436; 4,469,103; 4,375,220; 3,901,224; USSR 1329-781-A;and USSR 281489.

SUMMARY OF THE INVENTION

The present invention is a method and apparatus for thermally ablatinghollow body organs in order to deactivate the function of the organ,usually by inducing fibrosis of the interior of the organ and eventualresorption of the organ by the body. The method relies on introducing orentrapping a substantially unheated thermally conductive medium into theinterior of the hollow body organ and subsequently heating the medium toa temperature sufficient to destroy the endothelial lining or mucousmembrane. The thermally conductive medium will usually comprise anexternally introduced fluid, such as water, saline, contrast media, orthe like, but may also at least partly comprise a natural body fluid,such as blood, bile, urine, and the like. In some cases, the thermallyconductive medium may consist essentially of a natural body fluid whichhas been entrapped within the body organ.

Use of an unconstrained media allows heat to be transferred effectivelyto a convoluted interior surface of the hollow body organ. Usually, someor all ducts, passages, and the like, opening into the hollow body organwill be blocked in order to inhibit leakage of the medium during thetreatment procedure. The heating will be stopped after the desiredthermal injury has occurred, and the thermally conductive medium mayeither be aspirated or left within the organ. The organ will in mostinstances fibrose and be resorbed over time.

The introduction or entrapment of a substantially unheated thermallyconductive medium minimizes the risk of injury to tissue, organs, andother body structures surrounding the hollow body organ being treated,as well as to medical personnel administering the treatment. The use ofa radiologically detectable thermally conductive fluid such as contrastmedia allows visual confirmation that the medium is contained within thedesired body organ and is not subject to leakage prior to heating of themedium.

The apparatus of the present invention comprises a catheter including anelongate member having proximal and distal ends with a heating meansmounted near the distal end. The heating means is exposed to the fluidenvironment surrounding the distal end of the catheter and is thus ableto directly heat the thermally conductive medium which has beenintroduced to the hollow body organ. Conveniently, the catheter includesa lumen or other means for introducing the thermally conductive medium.Thus, the catheter may be introduced into the interior of the hollowbody organ and utilized both for introducing a thermally conductivemedium and for heating the medium to ablate the lining of the organ.Usually, the catheter will also include one or more inflatable balloonsor other means for sealing ducts or other passages communicating withthe hollow body organ. The catheter is introduced in such a way that theballoons are disposed within the ducts or passages and by then inflatingthe balloons, the desired sealing of the hollow body organ may beachieved.

Optionally, the catheter may be repositioned during a treatmentprocedure in order to control the amount of heat delivered to certainregions of the organ and connecting duct(s). In particular, the cathetermay first be inserted well into the duct so that a limited amount ofheat sufficient to injure the endothelial lining of the duct (but notexcessive to result in damage to surrounding tissue) may be delivered.The catheter may then be moved to expose the heating element to the mainvolume of the hollow body organ so that a substantially greater amountof heat may be delivered without causing damage to the tissuesurrounding the duct.

In a specific embodiment, the elongate member is flexible to facilitateintroduction into the hollow body organ and optionally into connectingducts and passages. The heating means is located proximally or distallyto the balloon or other sealing means and extends over a predeterminedlength, typically at least about 3 mm, usually from about 3 mm to 6 cm,more usually from about 1 cm to 4 cm, and most usually from about 1.5 cmto 3 cm. To further facilitate introduction and placement of thecatheter, the heating means is adapted to conform to the flexure of theelongate member, where such flexibility is of particular advantage whenthe catheter is to be placed into relatively constricted ducts orpassages which connect with the hollow body organ. Flexible heatingmeans able to conform to bending of the elongate member may comprise acoil heating element, a series of relatively small, discrete heatingelements distributed over said predetermined length, or the like.

In a preferred aspect of the present invention, the heating means isfurther adapted to deliver a nonlinear heat flux pattern over its axiallength. The heat flux pattern, in turn, may be selected to provide adesired heating profile within the fluid environment surrounding thedistal end of the catheter. In this way, heating of the fluidenvironment may be "programmed" to provide the proper amount of heat toeach region within the hollow body organ and optionally the connectingduct(s). Usually, a lesser heat flux will be directed within smallregions, such as a connecting duct, where the reduced volume of thefluid environment will allow the desired treatment temperature to beattained with the application of less heat. Greater heat flux may besimultaneously provided to the larger regions of the hollow body organwhich require greater total amounts of heat to reach the desiredtreatment temperature. Treatment of both the hollow body organ andconnecting region(s) may thus be performed in a single step without theneed to reposition the catheter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a thermal ablation catheter constructedin accordance with the principles of the present invention.

FIG. 2 is a detailed elevational view of the distal end of the catheterof FIG. 1 shown in cross-section.

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view taken along line 4--4 of FIG. 2.

FIG. 5 is a detailed elevational view of the distal end of the catheterhaving two inflation balloons spaced-apart at its distal end shown incross-section.

FIG. 6 is a cross-sectional view taken along line 6--6 of FIG. 5.

FIG. 7 is a cross-sectional view taken along line 7--7 of FIG. 5.

FIGS. 8A-8H illustrate the method of the present invention used in thethermal ablation of a gallbladder.

FIG. 9 illustrates the method of the present invention used in thethermal ablation of a segment of a blood vessel.

FIG. 10 is a perspective view of a thermal ablation catheter having aflexible heating source constructed in accordance with the principles ofthe present invention.

FIG. 11 is an elevational view of the distal end of a thermal ablationcatheter having a heating source capable of delivering a non-linear heatflux over its length.

FIG. 12 is an elevational view of the distal end of an alternativeembodiment of a catheter having a heat source capable of delivering anon-linear heat flux.

FIG. 13 illustrates the method of the present invention utilizing thecatheter of FIG. 12 in ablating a gallbladder and a portion of theconnecting cystic duct.

FIG. 14 is an elevational view of the distal end of a thermal ablationcatheter having a single inflatable balloon disposed proximally of theheating element.

FIG. 15 illustrates the method of the present invention utilizing thecatheter of FIG. 14 for ablating a kidney and portion of the connectingureter.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

The present invention is useful for ablation of a wide variety of hollowbody organs and body passages which have an endothelial lining, mucousmembrane, or other internal surface which may be thermally injured toinactivate the organ and usually to induce necrosis and subsequentfibrosis of the surrounding tissue. Exemplary hollow body organs includethe gallbladder, the appendix, the uterus, the kidney, and the like.Exemplary hollow body passages include blood vessels, fistulas, and thelike. Usually, the hollow body organs and body passages will be diseasedor in some way abnormal prior to ablation according to the presentinvention. In some cases, however, it may be desirable to ablate anddestroy apparently healthy body organs or parts in order to achieve adesired purpose, e.g., blockage of a blood vessel in a varicoceleprocedure. For convenience hereinafter, the phrase "hollow body organ"is intended to embrace both hollow body organs and hollow body passages.

The method of the present invention relies on introducing a thermallyconductive medium into the interior of the hollow body organ in such away that the organ is filled with the medium and the medium is in goodthermal contact with substantially the entire interior surface of theorgan. In this way, by heating the medium as will be describedhereinafter, the temperature of the endothelial lining or mucousmembrane of the body organ can be raised to a preselected temperaturefor a preselected minimum time period in order to permanently injure thelining and deactivate the organ, typically by inducing necrosis. Thethermally conductive medium can be virtually anyphysiologically-compatible liquid, solution, slurry, gel, and the like,which may be percutaneously or directly introduced into the interior ofthe hollow body organ. Exemplary thermally conductive media includewater, saline, contrast medium, physiological irrigating solution, andthe like.

As used herein, the term "ablation" means any injury or damage to thehollow body organ and/or connecting ducts and body passages whichresults in deactivation of the function of the organ, usually resultingin necrosis and eventual resorption of the organ. The resorption willtypically occur over an extended period of weeks, months, or longer.

The thermally conductive medium will be introduced to the interior ofthe hollow body organ at a temperature below that which will have adeleterious effect on the tissue and organs surrounding the hollow bodyorgan being treated. The temperature will be below about 60° C., usuallybeing below about 45° C., and more usually being at body temperature(37° C.) or room temperature (about 20° C.). In some cases, however, itmay be desirable to introduce the contrast medium above bodytemperature, usually in the range from about 37° C. to 45° C., in orderto shorten the time necessary to raise the temperature of the medium tothe treatment temperature, discussed hereinafter.

In order to induce necrosis of the endothelial lining or mucous membraneof the hollow body organ, the temperature of the thermally conductivemedium will be raised and maintained above a threshold level whichresults in injury to the endothelial mucous membrane. The thresholdtemperature will generally be above 45° C., usually being in the rangefrom 45° C. to 120° C., more usually being in the range from 65° C. to100° C., and preferably being in the range from about 70° C. to 90° C.Depending on the precise temperature employed and on the nature of theparticular organ being treated, the thermally conductive medium will bemaintained above the threshold temperature for a period of time in therange from about 1 to 60 minutes, usually being in the range from about1 to 30 minutes, more usually being in the range from about 2 to 20minutes, and preferably being in the range from about 2 to 10 minutes.Usually, the temperature of the thermally conductive medium will beraised as rapidly as possible and maintained at a substantially constanttreatment temperature for the desired treatment period. Alternatively,the treatment temperature may be varied during the treatment period withthe total treatment time being adjusted to take the variation intemperature into account.

Frequently, it will be desirable to control the amount of heat or heatflux being delivered to any particular region within the hollow bodyorgan and connecting duct(s) being treated. It will be appreciated thatthe temperature of the thermally conductive medium within the organ is afunction of both the heat flux being delivered and the volume ofthermally conductive medium surrounding the area where heat is beingapplied. Thus, for hollow body organs which have a non-uniform crosssectional area, the volume will vary over the length of the organ andthe temperature at any given point within the medium may deviatesubstantially from the average. In some cases therefore, it will bedesirable or necessary to control the rate of heat being delivered (i.e.heat flux) at any particular location within the hollow body organ andconnecting duct(s) to assure that the temperature within the desiredrange is reached (either simultaneously or at different times) at alllocations being treated. As described in more detail hereinafter, suchcontrolled or programmed heat delivery may be accomplished bypositioning a relatively small heating element for different amounts oftime at various locations within the hollow body organ in order toattain generally uniform heat treatment throughout. Alternatively, byemploying a heat delivery system which can provide for a non-linear heatflux over at least a portion of the length, uniform heat treatment ofthe hollow body organ can be obtained in a single application of heatwithout repositioning the catheter.

After the hollow body organ has been treated with the heated thermallyconductive medium at a temperature and for a time sufficient todeactivate the body organ and/or induce necrosis of the endotheliallining or mucous membrane of the organ, the thermal energy beingdelivered to the medium will be terminated. The thermally conductivemedium may then be aspirated from the hollow body organ, typically usingthe same catheter which was employed to deliver the medium and raise thetemperature of the medium as described above. Usually, however, thethermally conductive medium will not be aspirated until the temperaturehas decreased sufficiently so that its withdrawal will not exposetissues and organs surrounding the catheter to risk. Normally thewithdrawal temperature will be below about 55° C., preferably beingbelow about 45° C. Alternatively, the thermally conductive medium can beleft within the hollow body organ where it will be resorbed oreliminated by normal physiological processes.

The catheter of the present invention comprises an elongate memberhaving proximal and distal ends. The elongate member may be flexible orrigid, although flexible catheters are preferred for most applications.The length of the catheter will vary depending on the application withshort, rigid catheters typically having a length in the range from about10 to 20 cm, and long flexible catheters typically having a length inthe range from about 20 to 40 cm. Rigid elongate members may be formedfrom metals, typically stainless steel, rigid plastics, and the like,while flexible elongate members will typically be formed from extrudedorganic polymers, such as silicone rubber, polyurethane, polyvinylchloride, nylon, and the like. Elongate members will typically include amultiplicity of lumens to provide for fluid communication between theproximal end (outside the patient) to the distal end (inside thepatient). Normally, a lumen will be provided for delivering and/oraspirating the thermally conductive medium to the hollow body organ.Additional lumens may be provided for inflation of one or more balloons,for delivery of the catheter over a movable guidewire, for venting thehollow body organ while the thermally conductive medium is beingdelivered, and the like.

A heating means for raising the temperature of the fluid environmentsurrounding the distal end of the catheter will be provided at or nearthe distal tip of the elongate member typically being within about 10cm, more typically being within about 5 cm. The heating means willgenerally provide a heated surface for convectively heating fluidsurrounding the catheter tip, typically comprising a resistive heater, aradiating block heated by laser energy, or the like. Preferably, theheated surface will be exposed directly to the environment surroundingthe catheter, with a minimum amount of insulation covering the surface,in order to enhance heat transfer. The heating means may alternativelycomprise a microwave emitter capable of heating the fluid directly or aradiofrequency heating element. In some cases, it may also be possibleto heat the thermally conductive medium using dispersed laser radiation.In that case, it will be desirable to color or dye the thermallyconductive medium so that it can absorb radiation at the wavelength ofthe laser source.

A system will be provided for controlling the temperature to which thethermally conductive medium is heated by the heating means. Such atemperature control system may comprise a feedback controller where atemperature sensing element (typically a thermocouple or thermistor) ismounted on the catheter at a location chosen to accurately measure theheated environment surrounding the catheter, and the energy delivered tothe heating means is regulated based on the measured temperature of themedium. Alternatively, numerous autoregulating heaters are availablewhich do not require a separate control loop.

The heating means may comprise a single point heating source, forexample a single cartridge heater, extending over a limited distance,usually 3 mm or less. Often, however, it is desirable to provide adistributed heating source over an extended axial length greater than 3mm, usually being in the range from from about 3 mm to 6 cm, moreusually being in the range from about 1 cm to 4 cm, and most usuallybeing in the range from about 1.5 cm to 3 cm. Such elongate heatingsources will preferably be flexible over their length when mounted onflexible elongate members. In this way, the desired flexibility of thecatheter will not be substantially diminished by the heating source. Inparticular, the heating source itself will be able to be inserted intoconstricted, relatively tortuous, ducts and passages connecting with thehollow body organ.

Flexible elongate heating sources will typically comprise either aplurality of spaced-apart discrete heating elements, e.g. a plurality ofsingle point heating sources such as cartridge heaters, or acontinuously wound heating source, such as a heating coil wrapped aroundthe exterior of the flexible elongate member. In either case, it willoften be desirable to adapt the axially elongated heating source todeliver a variable heat flux over its length. In particular, the heatflux may be reduced in regions where the heating source will be within arestricted volume of thermally conductive medium and relativelyincreased where the heating source will be in a larger volume ofthermally conductive medium. In this way, a relatively uniformtemperature profile within the hollow body organ and optionallyconnecting ducts may be achieved.

Usually, the catheter will include at least one inflatable balloon foroccluding a duct or passage which would otherwise allow drainage of thethermally conductive medium from the hollow body organ during the courseof the treatment. At least one balloon will generally be located nearthe distal tip of the elongate member of the catheter and will beinflatable through an inflation lumen running through the catheter fromthe distal to the proximal end thereof. For many applications it will bedesirable to inflate the occluding balloon with a thermally conductivemedium, frequently the same medium used to fill the hollow body organ,so that the area in contact with the balloon will be heated andnecrosed. Optionally, means for heating the medium within the balloon toa temperature sufficient to induce necrosis in the endothelial lining ormucous membrane surrounding the inflated balloon may be provided. Suchheating means may be formed separately from or together with the meansused to heat the unconstrained thermally conductive medium.Alternatively, a thermally insulating medium such as carbon dioxide maybe used to inflate the balloon when it is desired to protect thesurrounding tissue and organs.

One or more additional inflatable balloons may also be provided in orderto seal other passages communicating with the hollow body organ. Forexample, a second inflatable balloon may be located on a side of theheating element opposite to that of the first heating element. The firstand second balloons may then be used to define a volume to be treatedtherebetween. Other balloon configurations may also be used for trappingthe thermal media in a particular hollow body organ or portion of ahollow body organ.

Although inflatable balloons will find the greatest use, other means forsealing or occluding a connecting duct or region may also be utilized.In particular, it will be possible to modify the distal tip of thecatheter so that it may be lodged within the duct or region to providethe desired seal. For example, the tip may be tapered or expanded sothat it will conform to the geometry of the duct or passage. Othermodifications may be based on the geometry of the organ being treated.

Referring now to FIGS. 1-4, a catheter 10 comprises an elongate flexiblebody 12 having a proximal end 14 and a distal end 16. The elongatemember 12 includes a plurality of axial slots 18 formed at or near thedistal end 16 and a heating element 20 disposed within the slots. Theheating element 20 is of a type which provides a heated externalsurface, typically being a resistive heating element where a pair ofwires 22 are run from the heating element to the proximal end 14 of thecatheter where they are taken out through a sealed port 23 in a proximalhousing 24. The wires 22 will typically be run through a central lumen26 and will be connected to a suitable power supply (not shown) forheating the heating element 20 to a desired temperature.

The central lumen 26 extends from the proximal end 14 of the elongatemember 12 and terminates at the proximal end of heating element 20 (FIG.2). A plurality of radial passages 28 (FIG. 2) are provided between thedistal end of the central lumen 26 and the proximal end of the heater20, which passages open into the axial slots 18. The proximal end ofcentral lumen 26 is connected through a side port 30 on the proximalhousing 24. In this way, thermally conductive medium may be deliveredthrough the central lumen 26 past the heating surface of heating element20 and into the hollow body organ. The thermally conductive media isthus rapidly heated as it passes the heater 20 into the hollow bodyorgan.

The catheter 10 also includes an inflatable balloon 34 at its distaltip. The balloon 34 may be inflated through inflation lumen 36 whichextends from an inflation port 38 on housing 24 to an outlet port 40communicating directly with the interior of the balloon 34. The balloon34 will usually be inflated with a heat conductive medium which will beheated by conduction from the heated fluid trapped by the balloon withinthe hollow body organ. An optional system (not illustrated) for heatingthe balloon within the medium may be provided. Systems for heatinginflation medium within a balloon are described in U.S. Pat. No.4,754,752, the disclosure of which is incorporated herein by reference.

A third lumen 42 is formed in a tubular extension 43 disposed in centrallumen 26. Lumen 42 extends through the distal tip of the catheter 10 andis axially-aligned with a lumen 45 (FIG. 3) through the heater 22. Thetubular extension 43 is usually separated from the main portion offlexible body 12 and attached to the heater (not illustrated) to allowthermally conductive fluid to flow unobstructed from the central lumen26 past the heater 22 and through the slots 18. Together, the lumens 42,43, and 45 are intended to form a fluid tight passage which can receivea movable guidewire which can be used to facilitate placement of thecatheter 10 within the desired hollow body organ, as described in moredetail hereinafter.

Referring now to FIGS. 5-7 and 9, a catheter 50 which is similar tocatheter 10 but includes a pair of spaced-apart inflation balloons 52and 54 is illustrated. The catheter 50 includes an elongate flexiblemember 56, a heating element 58, and is generally constructed asdescribed previously for catheter 10. The catheter 50, however, includesthe second inflatable balloon 54 which is spaced-apart proximally fromthe first balloon 52, with the two balloons being disposed on oppositesides of heating element 58. In this way, the two balloons 52 and 54 areable to isolate a volume therebetween which includes the heater 58. Byintroducing the thermally conductive medium between the two balloons 52and 54, the heater 58 may then be used to heat the isolated medium intreating a desired portion of a hollow body organ. The catheter 50includes first inflation lumen 60 to inflate the first balloon 52 and asecond inflation lumen 62 to inflate the second balloon 54. A centrallumen 64 serves both to introduce thermally conductive medium and toreceive a guidewire to facilitate placement of the catheter. Theguidewire may be received in a tubular extension (not illustrated) or aseal, such as an O-ring, may be provided to inhibit leakage of medium.Use of catheter 50 to ablate a region within a blood vessel BV isillustrated in FIG. 9. Such ablation will be useful in terminating theblood supply to a tumor, or to an arteriovenous shunt, or in otherprocedures where it is desired to block a blood vessel.

Referring now to FIGS. 8A-8H, the use of a two-balloon catheter of thetype illustrated in FIG. 5 for ablating a gallbladder will be described.Gallbladder ablation will be desirable in cases of cholecystolithiasiswhere the diseased gallbladder is likely to continue production of gallstones. Gallbladder ablation according to the present invention willgenerally be performed after the removal of gall stones by establishedleast invasive procedures, typically by either percutaneouscholecystostomy or by lithrotriptor.

The intact gallbladder is illustrated in FIG. 8A and includes a hollowsac structure connected to the cystic duct through the neck of thegallbladder. The cystic duct, in turn, is connected to the hepatic ductand common bile duct. The gallbladder is located on the lower (inferior)surface of the liver in a hollow (fossa) beneath the right lobe. Theupper (superior) surface of the gallbladder is attached to the liver byconnective tissue.

In treating the gallbladder according to the method of the presentinvention, a percutaneous guidewire 80 (FIG. 8B) is inserted into thegallbladder through the trans-hepatic route and into the common bileduct. A sheath 82 (FIG. 8C) is then placed over the guidewire 80 toprovide for access into the interior of the organ. The catheter 50 maythen be inserted over the guidewire 80 and positioned so that the firstballoon 52 lies beyond the neck of the gallbladder and just proximal tothe junction between the hepatic duct and the common duct (FIG. 8D). Thesecond balloon 54 will remain within the sheath 82, while the heater 58is located within the main body of the gallbladder.

After the catheter 50 is in place, the thermally conductive medium 84 isintroduced into the interior of the gallbladder through the catheter(FIG. 8E). The medium 84 is introduced until the main sac is entirelyfilled, as illustrated in FIG. 8F, and the first and second balloons 52and 54 are inflated in order to inhibit loss of the medium through thecystic duct and the sheath 82. During the introduction of the thermallyconductive medium to the gallbladder, it may be necessary to adjust theposition of the patient in order to expel trapped gases 86 (FIG. 8E).The gases 86 may be released through either the cystic duct or thesheath 82, or may be vented through a specially provided vent (notillustrated) within the catheter 50.

Once the main sac of the gallbladder is completely filled with thermallyconductive medium 84 (which may be confirmed by fluoroscopic examinationif a radiopaque medium is used), the heating element 58 will beactivated to raise the temperature of the medium, either by convection,radiation, or high frequency heating (FIG. 8G). Optionally, thethermally conductive medium 84 may have been partially heated by theheating element 58 as the medium is introduced by the catheter 50. Heatwill be conducted from the interior of the organ through the thermallyconductive media in the first balloon 52 in order to necrose theendothelial lining of the cystic duct in order to assure that thegallbladder lining will not regenerate. Usually, the second balloon 54will be inflated with a thermally insulating medium to protect the liverfrom the heat of the medium 84.

After maintaining the temperature of the heat conductive medium 84 (andoptionally the inflation medium with balloon 52) at the desired ablationtemperature for a sufficient time to completely necrose the endotheliallining of the gallbladder, the heating element 58 may be deenergized.

After allowing cooling, the thermally conductive medium 84 may beaspirated through the catheter or optionally through the sheath 82 afterballoon 54 has been deflated (FIG. 8H). Alternatively, the thermallyconductive medium 84 may be left within the main sac of the gallbladderfrom which it will eventually drain through the cystic duct and beeliminated by normal physiologic processes.

After about six weeks, the endothelial lining of the gallbladder will becompletely necrotic. The inflammation process will completely replacethe lining of the gallbladder with fibrotic tissue within about twelveweeks and the organ will start to resorb.

Referring now to FIG. 10, the construction of an alternative embodiment70 of the thermal ablation catheter of the present invention will bedescribed. The catheter 70 is constructed similarly to the catheter 10,described above, and includes an elongate flexible member 72 having aproximal end 74 and a distal end 76. An inflatable balloon 78 isdisposed at the distal end 76 of the elongate member 72, and a heatingsource 80 is located proximal to the balloon 78. The heating source 80is axially elongated and will be disposed over the exterior of themember. The heating source 80 will cover an axial length L of at leastabout 3 mm, usually being in the range from about 3 mm to 6 cm, moreusually being in the range from about 1 to 4 cm, and will most usuallybe in the range from about 1.5 cm to 3 cm. A perfusion port 83 isprovided between the balloon 78 and heating source 80 to deliver athermally conductive medium to the hollow body organ during a treatmentprocedure. The location of the perfusion port is not critical, and theport, for example, could also be located on the proximal side of heatingsource 80, or elsewhere so long as it is able to deliver thermallyconductive medium to a desired location in the body organ and/orconnecting region(s). A balloon inflation port 85 is provided interiorlyto balloon 78 in order to allow inflation of the balloon.

Fitting 86 is provided at the proximal end 74 of elongate member 72.Fitting 86 includes a first connector 88 which is fluidly coupled toballoon inflation port 85 through an inflation lumen (not illustrated)in the elongate member 72. A second connector 90 is provided forinserting a guidewire 92 through a central guidewire lumen (notillustrated) in elongate member 72. A third connector 94 is connected toperfusion port 83 through a third lumen (not illustrated) in theelongate member 72. Additionally, power leads 96 are provided forconnecting heat source 80 to an external power source (not illustrated)typically a current source for powering the resistance heater.

The heating source 80 is formed as an exterior winding or coil on thedistal end 76 of the elongate member 72. Typically, the coil 80 will behelically wound, but other patterns will also be suitable. The windingswill conveniently be formed from insulated resistance heating wire,where the biocompatible insulation is selected to be able to withstandthe physiologic conditions present in the hollow body organ beingtreated. The total length, number of turns in a particular location,electrical resistivity, and the like, of the wire used for the coil willbe selected to provide the desired heating flux delivery capability forthe heating source 80. As illustrated, the windings of heating source 80are uniform over the entire length L, but it will also be possible toprovide for a non-uniform winding density when it is desired to vary theheat flux delivery capability over the length of the heat source.

Referring now to FIG. 11, a particular embodiment 100 intended fornon-linear heat flux delivery is illustrated. Catheter 100 includes aplurality of spaced-apart coils 102, 104, and 106, over length L. Asillustrated, coil 102 located closest to the distal end of catheter 100includes the fewest windings, with coil 104 having more windings, andcoil 106 having the most windings. In this way, the heat flux deliveredby catheter 100 will increase over length L in the proximal direction.Such heat flux delivery could be programmed in the opposite way so thatthe flux will increase in the distal direction, or it could beprogrammed in virtually any other desired pattern. It would also bepossible to use other types of heat sources, such as point sourcesincluding cartridge heaters.

A heater 110 is provided within an inflation balloon 112. In this way,heat flux may be provided through the inflatable balloon 112 to thesurface of a duct or connecting passage which is being blocked. Byproperly balancing the heat flux delivery within balloon 112 with theheat flux delivery proximal to balloon 112, simultaneous ablation of ahollow body organ and connecting duct or passage may be achieved in asingle treatment step.

An alternative embodiment 120 of a catheter capable of delivering anon-linear heat flux is illustrated in FIG. 12. Instead of discrete,spaced apart coils as illustrated in FIG. 11, catheter 120 includes acontinuous coil 122 over length L, where the coil has a variable helicalpitch. By properly selecting the pitch, the heat flux at any point alonglength L can be selected to accommodate the intended use of catheter120. Although no heater is illustrated within inflation balloon 124 incatheter 120, a heat source could be provided, either as extension ofheating coil 122 or as a separate heating element.

The use of catheter 120 in the ablation of a gallbladder GB isillustrated in FIG. 13. The catheter 120 is introduced into thegallbladder GB and connecting cystic duct CD in a manner similar to thatdescribed in connection with FIGS. 8A-8H. The catheter 120 is insertedso that balloon 124 extends well into the cystic duct CD, with theheating coil 122 extending from just proximally of the balloon 124through the constricted region of the cystic duct CD and into the mainbody of the gallbladder GB. The pitch of heating coil 122 is varied sothat a reduced heat flux will occur within the reduced diameter regionsof the cystic duct and an increased heat flux will occur in the largervolumes of the gallbladder body. In this way, the catheter 120 may bepositioned, as illustrated, with heat applied along the entire length ofthe heating coil 122 for a fixed period of time. At the end of the fixedperiod of time, the proper total amount of heat will be applied to eachregion within the gallbladder GB and connecting cystic duct CD so thatthe endothelial lining will be injured without excessive heat havingbeen applied to any localized area. The catheter 120 may then bewithdrawn, either with or without removal of the thermally conductivemedium.

Referring now to FIG. 14, an additional embodiment 130 of the thermalablation catheter of the present invention is illustrated. The catheter130 includes a heating coil 132 disposed distally to an inflatableballoon. Such a construction which includes only a single balloonproximal to the heating element is particularly suitable for retrogradeintroduction into a hollow body organ, as will be described inconnection with FIG. 15. The heating coil 132 is divided into twosections 136 and 138 with a perfusion port 140 located therebetween. Thespecific design of the heating coil, location of the perfusion port,dimensions of the catheter, and the like, may of course all be variedwithin the broad parameters described above. FIG. 14 is providedprimarily to illustrate an embodiment where the heat source is locateddistally to a single sealing means.

Catheter 130 is particularly suited for retrograde introduction to ahollow body organ through a connecting region or duct. In FIG. 15,catheter 130 is introduced into a kidney K through the ureter U, whereballoon 134 is positioned well back within the ureter while heatingelement 132 extends into the interior of the kidney. In particular, thedistal heating section 136 is located primarily within the kidney, whilethe proximal heating section 138 remains generally within the ureter. Byproperly sizing the respective heat outputs of each section 136 and 138,the catheter 130 can be used to simultaneously ablate both the kidneyand the exposed portion of the ureter in a single heating step.Conveniently, the perfusion port 140 is located to introduce thermallyconductive medium evenly into both the kidney and the ureter.

Although the foregoing invention has been described in detail forpurposes of clarity of understanding, it will be obvious that certainmodifications may be practiced within the scope of the appended claims.

What is claimed is:
 1. A method for ablating a hollow body organ, saidmethod comprising:entrapping a substantially unheated thermallyconductive medium within the hollow body organ, wherein said medium isgenerally unconstrained so that it is in direct contact with theinterior of the hollow body organ; and heating the thermally conductivemedium within the hollow body organ to a temperature and for a timesufficient to destroy the lining of said organ, whereby the organ willsubsequently fibrose and be resorbed over time.
 2. A method as in claim1, wherein the thermally conductive medium is at least partly comprisedof a natural body fluid.
 3. A method as in claim 2, wherein thethermally conductive medium consists essentially of a natural bodyfluid.
 4. A method as in claim 1, wherein the hollow body organ has atleast one connecting duct and wherein the step of entrapping comprisessealing the connecting duct.